A dura mater is an outermost membrane constituting a meninx between a skull and a brain, protects the brain and prevents leakage of a cerebral spinal fluid. The dura mater further covers a spinal cord to perform the similar functions. In a field of neurosurgery, various materials have been used for repairing dura maters.
For example, an allogenic graft of dura mater derived from human was a most-used material for repairing a dura mater. However, by using dura maters of human dead bodies, disease agents of Creutzfeldt-Jacob Disease (CDJ) were spread, so the use of human dura maters was significantly decreased. Further, there are following disadvantages: homology of the allogenic graft of dura mater derived from human is low; and provision thereof is limited.
Conventionally, a thigh muscle membrane from patient's own body and an artificial membrane composed of polytetrafluoroethlene and polyurethane polymer, e.g., Gore-Tex (registered trademark), have been used as a substitute film for a dura mater.
However, by using the artificial membrane, a chronic foreign-body reaction appears and handleability of the artificial membrane is low, so new biocompatible artificial membranes have been developed.
On the other hand, an amniotic membrane is a thin membrane part of placenta in uterus, which envelopes an embryo, and is disposed after birth of the baby.
An amniotic membrane has a basement membrane and no blood components, and it hardly causes rejecting reaction in case of being used for transplantation.
Further, an amniotic membrane reduces inflammatory reaction and accelerates repair of wounds, so it has been used, in a surgery field, to cover a burn injury part or to prevent organs from closing up after intraperitoneal surgery from a long time ago.
An amniotic membrane is a useful medical material capable of preventing fluid leakage and promoting the healing of wounds, so it is used as a prosthetic material of a urinary bladder, a urethra and a ureter (see Patent Document 1), as a medical material using a dense layer (collagen layer) of an amniotic membrane (see Patent Document 2) and as a substitute membrane, which is a layered body constituted by two collagen layers derived from an amniotic membrane and a sheet-shaped porous intermediate agent provided therebetween, for a cerebral dura mater, a pericardium, etc. (see Patent Document 3).
Patent Document 1: Japanese Patent Document No. P63-260549A
Patent Document 2: Japanese Patent Document No. P8-266613A
Patent Document 3: Japanese Patent Document No. P10-113384A